Checkpoint-inclusive resource allocation

ABSTRACT

A resource allocation service can provide for the limited redelivery of events for processing using a set of virtual resources. A customer can provide code for execution, and the service can allocate resource instances configured to execute the code in response to various events. The processing for an event may not be completed by a single resource instance. When a resource instance is to end processing, the instance can capture state information to be returned as checkpoint data for the event. When the processing result is received, the service determines whether checkpoint data was included, which functions as a request for further processing. The service can then place the event data back in an event queue for redelivery and additional processing. A customer can specify a time limit or a retry limit such that an event can only undergo up to a maximum amount of processing before the event is failed.

BACKGROUND

Users are increasingly performing tasks using remote computing resources, which may be offered through a shared-resource environment. This has many advantages, as users do not have to purchase and maintain dedicated hardware and software, and instead can pay for only those resources that are utilized at any given time, where those resources typically will be managed by a resource provider. Users can perform tasks such as storing data or executing applications using various types of resources offered by the resource provider. In some environments resources can be allocated on a task-specific basis. There can be limitations on the amount of time for which a resource can be allocated, or the processing of a task may not otherwise complete in a single allocation. In conventional systems this can require the entire task to be retried using another allocation, which can waste resource and increase cost to the customer.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments in accordance with the present disclosure will be described with reference to the drawings, in which:

FIG. 1 illustrates an example environment in which various embodiments can be implemented.

FIG. 2 illustrates an example resource environment for providing task-based resource allocation that can be used in accordance with various embodiments.

FIG. 3 illustrates an example resource fleet for managing virtual resources based at least in part upon checkpoint data that can be utilized in accordance with various embodiments.

FIG. 4 illustrates an example process for processing functions including allowance for redeliveries that can be utilized in accordance with various embodiments.

FIG. 5 illustrates an example process for determining whether to allow additional processing retries that can be utilized in accordance with various embodiments.

FIG. 6 illustrates example components of a computing device that can be used to implement aspects of the various embodiments.

DETAILED DESCRIPTION

In the following description, various embodiments will be described. For purposes of explanation, specific configurations and details are set forth in order to provide a thorough understanding of the embodiments. However, it will also be apparent to one skilled in the art that the embodiments may be practiced without the specific details. Furthermore, well-known features may be omitted or simplified in order not to obscure the embodiment being described.

Approaches in accordance with various embodiments provide for the limited redelivery of events for processing using a set of virtual resources. A customer can provide code for execution which can be registered as a function with a resource allocation service or other such offering. The service can allocate resource instances, such as virtual machines, that are configured to execute the customer code of the registered function in response to various customer events. It might be the case, however, that the processing for an event is not completed by a single resource instance. The service provider might provide a time limit for processing by each instance, and the registered function might not have processing completed by a single instance due to reaching the time limit or another ending occurrence, such as a code bug or a break point in the registered event. When a resource instance is to end processing, the instance can capture state information and return that state information, and/or other appropriate information, as checkpoint data for the event. When the event processing result data is received, the service can determine whether checkpoint data was received as well. The inclusion of checkpoint data functions as a request for further processing. The service can then cause the event data and checkpoint data to be placed back in an event queue for redelivery and additional processing by another allocated resource instance, which could be the same or a different instance. In order to prevent resources being tied up by continual redelivery requests, a customer can specify a time limit or retry limit such that an event can only undergo a limited amount of processing before the event is failed.

Various other functions can be implemented within the various embodiments as well as discussed and suggested elsewhere herein.

FIG. 1 illustrates an example environment 100 in which aspects of the various embodiments can be implemented. In this example a user is able to utilize a client device 102 to submit requests across at least one network 104 to a resource provider environment 106. The client device can include any appropriate electronic device operable to send and receive requests, messages, or other such information over an appropriate network and convey information back to a user of the device. Examples of such client devices include personal computers, tablet computers, smart phones, notebook computers, and the like. The at least one network 104 can include any appropriate network, including an intranet, the Internet, a cellular network, a local area network (LAN), or any other such network or combination, and communication over the network can be enabled via wired and/or wireless connections. The resource provider environment 106 can include any appropriate components for receiving requests and returning information or performing actions in response to those requests. As an example, the provider environment might include Web servers and/or application servers for receiving and processing requests, then returning data, Web pages, video, audio, or other such content or information in response to the request.

In various embodiments, the provider environment may include various types of resources that can be utilized by multiple users for a variety of different purposes. In at least some embodiments, all or a portion of a given resource or set of resources might be allocated to a particular user or allocated for a particular task, for at least a determined period of time. The sharing of these multi-tenant resources from a provider environment is often referred to as resource sharing, Web services, or “cloud computing,” among other such terms and depending upon the specific environment and/or implementation. In this example the provider environment includes a plurality of resources 114 of one or more types. These types can include, for example, application servers operable to process instructions provided by a user or database servers operable to process data stored in one or more data stores 116 in response to a user request. As known for such purposes, the user can also reserve at least a portion of the data storage in a given data store. Methods for enabling a user to reserve various resources and resource instances are well known in the art, such that detailed description of the entire process, and explanation of all possible components, will not be discussed in detail herein.

In at least some embodiments, a user wanting to utilize a portion of the resources 114 can submit a request that is received to an interface layer 108 of the provider environment 106. The interface layer can include application programming interfaces (APIs) or other exposed interfaces enabling a user to submit requests to the provider environment. The interface layer 108 in this example can also include other components as well, such as at least one Web server, routing components, load balancers, and the like. When a request to provision a resource is received to the interface layer 108, information for the request can be directed to a resource manager 110 or other such system, service, or component configured to manage user accounts and information, resource provisioning and usage, and other such aspects. A resource manager 110 receiving the request can perform tasks such as to authenticate an identity of the user submitting the request, as well as to determine whether that user has an existing account with the resource provider, where the account data may be stored in at least one data store 112 in the provider environment. A user can provide any of various types of credentials in order to authenticate an identity of the user to the provider. These credentials can include, for example, a username and password pair, biometric data, a digital signature, or other such information. The provider can validate this information against information stored for the user. If the user has an account with the appropriate permissions, status, etc., the resource manager can determine whether there are adequate resources available to suit the user's request, and if so can provision the resources or otherwise grant access to the corresponding portion of those resources for use by the user for an amount specified by the request. This amount can include, for example, capacity to process a single request or perform a single task, a specified period of time, or a recurring/renewable period, among other such values. If the user does not have a valid account with the provider, the user account does not enable access to the type of resources specified in the request, or another such reason is preventing the user from obtaining access to such resources, a communication can be sent to the user to enable the user to create or modify an account, or change the resources specified in the request, among other such options.

Once the user is authenticated, the account verified, and the resources allocated, the user can utilize the allocated resource(s) for the specified capacity, amount of data transfer, period of time, or other such value. In at least some embodiments, a user might provide a session token or other such credentials with subsequent requests in order to enable those requests to be processed on that user session. The user can receive a resource identifier, specific address, or other such information that can enable the client device 102 to communicate with an allocated resource without having to communicate with the resource manager 110, at least until such time as a relevant aspect of the user account changes, the user is no longer granted access to the resource, or another such aspect changes.

The resource manager 110 (or another such system or service) in this example can also function as a virtual layer of hardware and software components that handles control functions in addition to management actions, as may include provisioning, scaling, replication, etc. The resource manager can utilize dedicated APIs in the interface layer 108, where each API can be provided to receive requests for at least one specific action to be performed with respect to the data environment, such as to provision, scale, clone, or hibernate an instance. Upon receiving a request to one of the APIs, a Web services portion of the interface layer can parse or otherwise analyze the request to determine the steps or actions needed to act on or process the call. For example, a Web service call might be received that includes a request to create a data repository.

An interface layer 108 in at least one embodiment includes a scalable set of customer-facing servers that can provide the various APIs and return the appropriate responses based on the API specifications. The interface layer also can include at least one API service layer that in one embodiment consists of stateless, replicated servers which process the externally-facing customer APIs. The interface layer can be responsible for Web service front end features such as authenticating customers based on credentials, authorizing the customer, throttling customer requests to the API servers, validating user input, and marshalling or unmarshalling requests and responses. The API layer also can be responsible for reading and writing database configuration data to/from the administration data store, in response to the API calls. In many embodiments, the Web services layer and/or API service layer will be the only externally visible component, or the only component that is visible to, and accessible by, customers of the control service. The servers of the Web services layer can be stateless and scaled horizontally as known in the art. API servers, as well as the persistent data store, can be spread across multiple data centers in a region, for example, such that the servers are resilient to single data center failures.

As mentioned, such an environment enables organizations to obtain and configure computing resources over a network such as the Internet to perform various types of computing operations (e.g., execute code, including threads, programs, software, routines, subroutines, processes, etc.). Thus, developers can quickly purchase or otherwise acquire a desired amount of computing resources without having to worry about acquiring physical machines. Such computing resources are typically purchased in the form of virtual computing resources, or virtual machine instances. These instances of virtual machines, which are hosted on physical computing devices with their own operating systems and other software components, can be utilized in the same manner as physical computers.

In many such environments, resource instances such as virtual machines are allocated to a customer (or other authorized user) for a period of time in order to process tasks on behalf of that customer. In many cases, however, a customer may not have a steady flow of work such that the customer must maintain a sufficient number of virtual machines to handle peak periods of work but will often have less than this amount of work. This can result in underutilization and unneeded expense for both the customer and the resource provider. Approaches in accordance with various embodiments can instead allocate resource instances or a task or event basis. A resource instance can be allocated in response to a customer request or event, and once the processing is complete that instance can either be made available for processing a different event or destroyed, among other such options. In either case, the customer will not be charged for more processing by the instance than was needed for the particular request or event.

FIG. 2 illustrates components of an example environment 200 that can be used to implement such functionality. The functionality can be offered as a service, such as a Web service, in at least some embodiments, wherein a client device 202 associated with a customer can submit requests or event information over at least one network 204 to the resource environment (i.e., a resource provider environment, service provider environment, or other shared resource or multi-tenant environment). The events or requests can each be associated with specific code to be executed in the resource environment. This code can be registered with the system, and will be referred to herein as a registered function owned by the respective customer. The compute service offered by the resource environment can be referred to as a “serverless” compute service that can allocate virtual resources to execute registered functions in response to customer events and automatically manage the underlying compute resources. The functions can be executed on high-availability compute infrastructure that can perform the administration of the compute resources, including server and operating system maintenance, capacity provisioning and automatic scaling, code and security patch deployment, and code monitoring and logging. Customers supply the code to be executed and can be billed based on the actual amount of compute time utilized on behalf of those customers.

In some embodiments, a registered function can include the customer code as well as associated configuration information. The configuration information can include, for example, the function name and resource requirements. Registered functions can be considered to be “stateless,” with no affinity to the underlying infrastructure, so that the resource managers can rapidly launch as many copies of the function as is needed to scale to the rate of incoming events. A customer providing the code for a function can specify various configuration parameters, such as the memory, timeout period, and access rules, among other such aspects. The customer in some embodiments can also specify resources that are able to trigger execution of a registered function by a resource instance. These resources can include, for example, data buckets, database tables, or data streams, among other such options. The resource manager can invoke the code only when needed and automatically scale to support the rate of incoming requests without requiring configuration or management on behalf of the customer. A function can be executed by an allocated resource instance within milliseconds of an event in at least some embodiments, and since the service scales automatically the performance will remain consistently high as the frequency of events increases. Further, since the code is stateless the service can initialize as many resource instances as needed without lengthy deployment and configuration delays.

Routing information for customer requests or events to execute on a virtual compute fleet (e.g., a group of virtual machine instances that may be used to service such requests) based on the frequency of execution of the user code enables high frequency user code to achieve high distribution, which can be good for fault tolerance, and enables low frequency user code to achieve high consolidation, which can be good for cost reduction.

An environment such as that described with respect to FIG. 2 can facilitate the handling of requests to execute user code on a virtual compute fleet by utilizing the containers created on the virtual machine instances as compute capacity. Information for a request or event can be received to a load balancer 208 that can determine an appropriate resource fleet 210, 212 to which to direct the information. As will be discussed in more detail later herein, the decision can be based upon various types of information, as may include the context associated with the type of event or request. Upon receiving a request to execute user code on the a selected virtual compute fleet 210, 212, a frontend service 214, 222 associated with the virtual compute fleet can provide the information to an instance manager, which can direct the information to a virtual machine (VM) instance 218, 220, 226, 228 where a container on the instance can provide an execution environment for the registered function.

The client device 202 may utilize one or more user interfaces, command-line interfaces (CLIs), application programming interfaces (APIs), and/or other programmatic interfaces for generating and uploading customer code, invoking the customer code (e.g., submitting a request to execute the code on the virtual compute system), scheduling event-based jobs or timed jobs, tracking the customer code, and/or viewing other logging or monitoring information related to their requests and/or customer code. Although one or more embodiments may be described herein as using a user interface, it should be appreciated that such embodiments may, additionally or alternatively, use any CLIs, APIs, or other programmatic interfaces.

In the example of FIG. 2, the resource environment 206 is illustrated as being connected to at least one network 204. In some embodiments, any of the components within the recourse environment can communicate with other components (e.g., client computing devices 202 and auxiliary services 230, which may include monitoring/logging/billing services, storage service, an instance provisioning service, and/or other services that may communicate with components or services of the resource environment 206. In other embodiments, only certain components such as the load balancer 208 and/or the frontends 214, 222 may be connected to the network 204, and other components of the virtual resource service (i.e., components of the resource fleets) may communicate with other components of the resource environment 206 via the load balancer 208 and/or the frontends 214, 222.

Customer may use the resource fleets 210, 212 to execute user code thereon. For example, a customer may wish to run a piece of code in connection with a web or mobile application that the customer has developed. One way of running the code would be to acquire virtual machine instances from service providers who provide infrastructure as a service, configure the virtual machine instances to suit the customer's needs, and use the configured virtual machine instances to run the code. Alternatively, the customer may send the resource service a code execution request. The resource service can handle the acquisition and configuration of compute capacity (e.g., containers, instances, etc., which are described in greater detail below) based on the code execution request, and execute the code using the compute capacity. The allocation may automatically scale up and down based on the volume, thereby relieving the customer from the burden of having to worry about over-utilization (e.g., acquiring too little computing resources and suffering performance issues) or under-utilization (e.g., acquiring more computing resources than necessary to run the codes, and thus overpaying).

In the configuration depicted in FIG. 2, a first resource fleet 210 includes a frontend 214, an instance manager 216 (later referred to herein as a worker manager), and virtual machine instances 218, 220. Similarly, other resource fleets 212 can also include a frontend 222, an instance manager 224, and virtual machine instances 226, 228, and there can be any appropriate number of resource fleets and any appropriate number of instances in each resource fleet. The environment can include low and high frequency fleets as well in at least some embodiments, as may serve different types of requests or requests for different types of customers. The fleets can also include any number of worker managers, and in some embodiments the frontend and the worker manager can be resident on a single virtual machine instance.

In some embodiments, the load balancer 208 serves as a front door to all the other services provided by the virtual compute system. The load balancer 208 processes requests to execute user code on the virtual compute system and handles the first level of load balancing across the frontends 214, 222. For example, the load balancer 208 may distribute the requests among the frontends 214, 222 (e.g., based on the individual capacity of the frontends). The requests can be distributed evenly across the frontends or distributed based on the available capacity on the respective fleets, among other such options.

Customer code as used herein may refer to any program code (e.g., a program, routine, subroutine, thread, etc.) written in a program language. Such customer code may be executed to achieve a specific task, for example, in connection with a particular web application or mobile application developed by the user. For example, the customer code may be written in JavaScript (node.js), Java, Python, and/or Ruby. The request may include the customer code (or the location thereof) and one or more arguments to be used for executing the customer code. For example, the customer may provide the customer code along with the request to execute the customer code. In another example, the request may identify a previously uploaded program code (e.g., using the API for uploading the code) by its name or its unique ID. In yet another example, the code may be included in the request as well as uploaded in a separate location (e.g., the external storage service or a storage system internal to the resource environment 206) prior to the request is received by the load balancer 208. The virtual compute system may vary its code execution strategy based on where the code is available at the time the request is processed.

In some embodiments, the frontend 214 for a fleet can determine that the requests are properly authorized. For example, the frontend 214 may determine whether the user associated with the request is authorized to access the customer code specified in the request. The frontend 214 may receive the request to execute such customer code in response to Hypertext Transfer Protocol Secure (HTTPS) requests from a customer, or user associated with that customer. Also, any information (e.g., headers and parameters) included in the HTTPS request may also be processed and utilized when executing the customer code. As discussed above, any other protocols, including, for example, HTTP, MQTT, and CoAP, may be used to transfer the message containing the code execution request to the frontend 214. The frontend 214 may also receive the request to execute such customer code when an event is detected, such as an event that the customer has registered to trigger automatic request generation. For example, the customer may have registered the customer code with an auxiliary service 230 and specified that whenever a particular event occurs (e.g., a new file is uploaded), the request to execute the customer code is sent to the frontend 214. Alternatively, the customer may have registered a timed job (e.g., execute the user code every 24 hours). In such an example, when the scheduled time arrives for the timed job, the request to execute the customer code may be sent to the frontend 214. In yet another example, the frontend 214 may have a queue of incoming code execution requests, and when the batch job for a customer is removed from the virtual compute system's work queue, the frontend 214 may process the customer request. In yet another example, the request may originate from another component within the resource environment 206 or other servers or services not illustrated in FIG. 2.

A customer request may specify one or more third-party libraries (including native libraries) to be used along with the customer code. In one embodiment, the customer request is a ZIP file containing the customer code and any libraries (and/or identifications of storage locations thereof) that are to be used in connection with executing the customer code. In some embodiments, the customer request includes metadata that indicates the program code to be executed, the language in which the program code is written, the customer associated with the request, and/or the computing resources (e.g., memory, etc.) to be reserved for executing the program code. For example, the program code may be provided with the request, previously uploaded by the customer, provided by the virtual compute system (e.g., standard routines), and/or provided by third parties. In some embodiments, such resource-level constraints (e.g., how much memory is to be allocated for executing a particular user code) are specified for the particular customer code, and may not vary over each execution of the customer code. In such cases, the virtual compute system may have access to such resource-level constraints before each individual request is received, and the individual requests may not specify such resource-level constraints. In some embodiments, the customer request may specify other constraints such as permission data that indicates what kind of permissions that the request has to execute the user code. Such permission data may be used by the virtual compute system to access private resources (e.g., on a private network).

In some embodiments, the customer request may specify the behavior that should be adopted for handling the customer request. In such embodiments, the customer request may include an indicator for enabling one or more execution modes in which the customer code associated with the customer request is to be executed. For example, the request may include a flag or a header for indicating whether the customer code should be executed in a debug mode in which the debugging and/or logging output that may be generated in connection with the execution of the customer code is provided back to the customer (e.g., via a console user interface). In such an example, the virtual compute system 110 may inspect the request and look for the flag or the header, and if it is present, the virtual compute system may modify the behavior (e.g., logging facilities) of the container in which the customer code is executed, and cause the output data to be provided back to the customer. In some embodiments, the behavior/mode indicators are added to the request by the user interface provided to the customer by the virtual compute system. Other features such as source code profiling, remote debugging, etc. may also be enabled or disabled based on the indication provided in the request.

The frontend 214 can receive requests to execute customer code on the virtual compute system that have been processed by the load balancer 208. The frontend 214 can request the instance manager 216 associated with the frontend 214 of the particular fleet 210 to find compute capacity in one of the virtual machine instances 218, 220 managed by the instance manager 216. The frontend 214 may include a usage data manager for determining the usage status (e.g., indicating how frequently the user code is executed) of a particular customer code, and a customer code execution manager for facilitating the execution of customer code on one of the virtual machine instances managed by the worker manager. The instance manager 216 manages the virtual machine instances in the respective fleet. After a request has been successfully processed by the load balancer 208 and the frontend 214, the instance manager 216 finds capacity to service the request to execute customer code on the virtual compute system. For example, if there exists a container on a particular virtual machine instance that has the user code loaded thereon, the instance manager 216 may assign the container to the request and cause the request to be executed in the container. Alternatively, if the customer code is available in the local cache of one of the virtual machine instances, the instance manager 216 may create a new container on such an instance, assign the container to the request, and cause the customer code to be loaded and executed in the container. Otherwise, the instance manager 216 may assign a new virtual machine instance to the customer associated with the request from the pool of pre-initialized and pre-configured virtual machine instances, download the customer code onto a container created on the virtual machine instance, and cause the customer code to be executed in the container.

In some embodiments, the virtual compute system is adapted to begin execution of the customer code shortly after it is received (e.g., by the load balancer 208 or frontend 214). A time period can be determined as the difference in time between initiating execution of the customer code (e.g., in a container on a virtual machine instance associated with the customer) and receiving a request to execute the customer code (e.g., received by a frontend). The virtual compute system can be adapted to begin execution of the customer code within a time period that is less than a predetermined duration. The customer code may be downloaded from an auxiliary service 230. The data may comprise user code uploaded by one or more customers, metadata associated with such customer code, or any other data utilized by the virtual compute system to perform one or more techniques described herein. Although only the storage service is illustrated in the example of FIG. 2, the resource environment 206 may include other levels of storage systems from which the customer code may be downloaded. For example, each instance may have one or more storage systems either physically (e.g., a local storage resident on the physical computing system on which the instance is running) or logically (e.g., a network-attached storage system in network communication with the instance and provided within or outside of the virtual compute system) associated with the instance on which the container is created. Alternatively, the code may be downloaded from a web-based data store provided by the storage service.

In some embodiments, once a virtual machine instance has been assigned to a particular customer, the same virtual machine instance cannot be used to service requests of any other customer. This provides security benefits to customers by preventing possible co-mingling of user resources. Alternatively, in some embodiments, multiple containers belonging to different customers (or assigned to requests associated with different customers) may co-exist on a single virtual machine instance. Such an approach may improve utilization of the available compute capacity. Although the virtual machine instances are described here as being assigned to a particular customer, in some embodiments the instances may be assigned to a group of customers, such that an instance is tied to the group of customers and any member of the group can utilize resources on the instance. For example, the customers in the same group may belong to the same security group (e.g., based on their security credentials) such that executing one member's code in a container on a particular instance after another member's code has been executed in another container on the same instance does not pose security risks. Similarly, the instance manager 216 may assign the instances and the containers according to one or more policies that dictate which requests can be executed in which containers and which instances can be assigned to which customers. An example policy may specify that instances are assigned to collections of customers who share the same account (e.g., account for accessing the services provided by the virtual compute system). In some embodiments, the requests associated with the same customer group may share the same containers (e.g., if the customer code associated therewith are identical). In some embodiments, a request does not differentiate between the different customers of the group and simply indicates the group to which the customers associated with the requests belong. In some embodiments, the virtual compute system may maintain a separate cache in which customer code is stored to serve as an intermediate level of caching system between the local cache of the virtual machine instances and a web-based network storage (e.g., accessible via the network 140).

The instance manager 216 may also manage creation, preparation, and configuration of containers within virtual machine instances. Containers can be logical units within a virtual machine instance and utilize resources of the virtual machine instances to execute customer code. Based on configuration information associated with a request to execute customer code, such a container manager can create containers inside a virtual machine instance. In one embodiment, such containers are implemented as Linux containers.

After the customer code has been executed, the instance manager 216 may tear down the container used to execute the user code to free up the resources it occupied to be used for other containers in the instance. Alternatively, the instance manager 216 may keep the container running to use it to service additional requests from the same customer. For example, if another request associated with the same customer code that has already been loaded in the container, the request can be assigned to the same container, thereby eliminating the delay associated with creating a new container and loading the customer code in the container. In some embodiments, the instance manager 216 may tear down the instance in which the container used to execute the customer code was created. Alternatively, the instance manager 216 may keep the instance running to use the instance to service additional requests from the same customer. The determination of whether to keep the container and/or the instance running after the user code is done executing may be based on a threshold time, the type of the user, average request volume of the user, and/or other operating conditions.

In some embodiments, the virtual compute system may provide data to one or more of the auxiliary services 230 as the system services incoming code execution requests. For example, the virtual compute system may communicate with the monitoring/logging/billing services, which may include: a monitoring service for managing monitoring information received from the virtual compute system, such as statuses of containers and instances on the virtual compute system; a logging service for managing logging information received from the virtual compute system, such as activities performed by containers and instances on the virtual compute system; and a billing service for generating billing information associated with executing customer code on the virtual compute system (e.g., based on the monitoring information and/or the logging information managed by the monitoring service and the logging service). In addition to the system-level activities that may be performed by the monitoring/logging/billing services (e.g., on behalf of the virtual compute system) as described above, the monitoring/logging/billing services may provide application-level services on behalf of the customer code executed on the virtual compute system. For example, the monitoring/logging/billing services may monitor and/or log various inputs, outputs, or other data and parameters on behalf of the customer code being executed on the virtual compute system. Although shown as a single block, the monitoring, logging, and billing services may be provided as separate services.

In some embodiments, the instance manager 216 may perform health checks on the instances and containers managed by the instance manager (e.g., an “active pool” of virtual machine instances managed by the instance manager and currently assigned to one or more customers). For example, the health checks performed by the instance manager 216 may include determining whether the instances and the containers managed by the instance manager have any issues of (1) misconfigured networking and/or startup configuration, (2) exhausted memory, (3) corrupted file system, (4) incompatible kernel, and/or any other problems that may impair the performance of the instances and the containers. In one embodiment, the instance manager 216 performs the health checks periodically. In some embodiments, the frequency of the health checks may be adjusted automatically based on the result of the health checks. In other embodiments, the frequency of the health checks may be adjusted based on customer requests. In some embodiments, the instance manager 216 may perform similar health checks on the instances and/or containers in the pool of pre-warmed virtual machine instances that are not yet assigned to any customer but ready to service incoming requests. The instances and/or the containers in such a warming pool may be managed either together with those instances and containers in the active pool or separately. In some embodiments, in the case where the health of the instances and/or the containers in the warming pool is managed separately from the active pool, a separate warming pool manager that manages the warming pool may perform the health checks described above on the instances and/or the containers in the warming pool.

The virtual machine instances can be logical in nature and implemented by a single or multiple physical computing devices. At least some of the virtual machine instances may be provisioned to provide a variety of different desired conditions depending on the needs of the user. Examples of the types of desired conditions include, but are not limited to: particular operating systems, particular language runtimes, and particular libraries that may be utilized by the user code. Additionally, one or more virtual machine instances may be provisioned generically when a desired operating condition is not specified or is otherwise not available. One skilled in the relevant art will appreciate that the virtual compute system is logical in nature and can encompass physical computing devices from various geographic regions.

The frontend 214, 222 can route code-processing requests according to a method that is different than the method used by the load balancer 208 to route requests among the frontends. For example, a frontend 214 can route the requests to the specific instance manager based on the customer code and/or based on the customer associated with the customer code. In some embodiments, the routing is determined based on a consistent-hashing scheme in which one or more parameters associated with the request (e.g., customer ID, customer code ID, etc.) are hashed according to a hash function and the request is sent to one of the instance managers that has previously been assigned to the sections of a hash ring (e.g., containing a plurality of hash values) that corresponds to the resulting hash value. For example, the instance managers can occupy one or more sections of the hash ring, and the requests can be mapped to those same hash values. In some embodiments, the hash values may be integer values, and each instance manager may be associated with one or more integer values. The one or more integer values associated with a particular instance manager may be determined based on one or more parameters associated with the instance manager (e.g., IP address, instance ID, etc.). In some embodiments, the request may be sent to the instance manager whose associated integer values are closest to, but not larger than, the hash value calculated for that request (e.g., using modulo arithmetic).

When the frontends determine that one or more instance managers have become unavailable, the frontends can associate the hash values previously associated with the one or more instance managers that have become unavailable with one or more available instance managers in another fleet. Similarly, when a new instance manager is added to a fleet, the new instance manager may take a share of the hash values associated with the existing instance managers. For example, the new instance manager may be assigned one or more sections of the hash ring that were previously assigned to the existing instance managers.

As mentioned, resource capacity can be allocated as needed to execute code or perform specific tasks, which can be allocated in response to various events. The events can include any appropriate types of events, as may be permitted by a service provider or allowed through various rules or policies, among other such options. These can include, for example, modifications to data buckets or updates to data tables, among other such options. The dynamic allocation of such capacity enables service owners to get out of the business of provisioning and managing the underlying hardware for executing code. For flexibility and efficiency in resource management, such a platform or service might not make any guarantees with respect to reusing the same containers or resource instances for running a specific instance of code, such as a registered function, for all incoming requests.

As mentioned, such a service or platform can utilize an event-driven data processing model wherein instances of functions are launched in response to a notification event, such as a data object being placed into a bucket or an update of a database table. A resource instance corresponding to a registered function can then be granted a limited amount (or determined period) of time to complete processing for each event. It is possible that the code being executed for a registered function may generate or encounter an error processing an event or be interrupted by the resource allocation service due to the service reaching an execution time limit. In some embodiments, the resource allocation service will redeliver the same event for up to a fixed number of times. If a customer of the service has functions which require a length of execution that exceeds the maximum allowed limit, the customer may have to build their own mechanism for recording event processing checkpoints and ensuring that all events receive enough execution cycles to be completely processed. The need for a customer to build and maintain such a mechanism considerably reduces the convenience and simplicity of using such a platform.

Accordingly, approaches in accordance with various embodiments can enable a function owner to optionally return checkpoint data, or another type of data object, etc., that can indicate that a redelivery is requested to be performed when the processing is interrupted due to a timeout or other such service criterion. The checkpoint data can contain information that the function can use to restore its internal state for processing the event, which corresponds to the state data for the function just prior to the interruption. When a function returns checkpoint data, the resource allocation system can determine that the function needs additional resource allocation in order to complete processing for the event. A resource manager, delivery manager, or other such component or service can then cause the event and its associated checkpoint data to be returned to the functions event queue for delivery at a next event execution cycle or allocation opportunity. When an event is to be pulled from the queue for processing, the resource manager can cause the associated checkpoint data to be delivered along with the event to the function. The process can repeat for an event until no checkpoint data is received for the event and, thus, no further event redelivery is requested by the function.

It might be the case, however, that a bug in the function or other such occurrence might cause the function to submit more redelivery attempts than are required, in some cases arising to an infinite number of requests. To avoid resource starvation due to such an occurrence, function owners (or other appropriate entities, such as a resource provider) can configure or specify the maximum number of redelivery requests for an event, or type of event. The service provider might also provide a maximum number of retries in some embodiments, or require that functions specify a maximum number of retries, among other such options. Function owners in some embodiments can also specify rules to adjust this threshold. For example, a maximum number of redelivery requests can be defined in relation to a number of events in the function queue and, in some cases, its utilization of maximum concurrent execution limit. In some embodiments, a function owner may also be able to specify a maximum length of time that a function may spend on processing an event from start to end, in order to avoid unnecessary continuation of processing a stale event. For example, a function owner might only be interested in processing an event within thirty minutes of the first reception or delivery of an event by the service. If the time elapsed from this starting point for an event is beyond a specified threshold, such as a thirty minute threshold, the customer may rather have the event processing discarded to save the customer's concurrent execution limit for newer events. This mechanism can be offered for any or all events in the queue, and not only the events scheduled for redelivery.

FIG. 3 illustrates an example environment 300 that can be used to implement at least some of this functionality. In this example, information for customer requests or events can be directed to a resource fleet 302. The information can be directed using a load balancer and/or interface layer as discussed previously as part of a resource provider environment. In this example the resource instances will be referred to as “workers,” which in various embodiments can refer to the virtual machine instances 218, 220, 226, 228 described with respect to FIG. 2. It should be understood, however, that various other types of resource instances can be utilized as workers as well within the scope of the various embodiments.

As described, the frontend 304 may receive an event notification, customer request, or other event information that indicates an event has occurred for which a registered function should be utilized or processing. In this example, the frontend 304 can determine the appropriate registered function and place the event information in an event queue 306. In other embodiments the event information might be placed into the event queue before determining the registered function, or the event information might specify the registered function, among other such options. Further, in this event the frontend 304 and/or a worker manager of the frontend can place the event information in the event queue 306, while in other embodiments other worker managers 312, 316 might receive the information and place the information in the same, or a different queue, among other such options. The frontend, worker manager, or a separate queue manager can determine that a worker 314 is now available to process the event information using the respective registered function. This can include, for example, determining that a new instance should be initialized to process the event as well as allocating an existing instance, etc. The respective worker manager 312 can then allocate the worker 312 for the event, pull the event information from the event queue 306, and provide the information to the allocated worker 314 for processing using the registered function.

At some subsequent point, the allocated worker 314 will complete processing for the event. This can occur for a number of different reasons as discussed elsewhere herein. For example, all processing for the event may have completed such that the result of the processing can be provided. In some instances, the processing may have reached a breakpoint wherein the processing by a particular instance might be completed. As mentioned, a customer might break up the processing in order to enable longer-running functions to be processed wherein the length of processing time exceeds the maximum time that any particular allocated instance can process event information. In other embodiments, the instance may have actually reached its maximum processing time, among other such options. Regardless of the reason in this example, the allocated instance can return a result of the processing that can be received back to the worker manager 312 and/or the frontend 304. In some embodiments the result will go to the worker manager, so the manager knows the instance is available for processing another event, and then can go to the frontend, so the frontend can determine if a redelivery is required.

The frontend 304 can analyze the response to determine whether any checkpoint data was returned with the event data. The checkpoint data can include any appropriate information as discussed elsewhere herein, such as state data for the allocated instance prior to completion of the processing. If there is no checkpoint data, then the frontend can determine that processing for the event has completed and can return the appropriate information or response indicating that the processing has completed, and providing any relevant result(s). If, however, checkpoint data was received with the event data, then the front end can determine that additional processing is required for the event. In this example, the frontend 304 can work with a delivery manager 310 to cause the event data to be placed back in the event queue 306 for subsequent redelivery to one of the workers 314 for processing. This can be the same or a different event queue, which may have the same or a different priority than the earlier queue. In some embodiments the checkpoint data will be stored with the event data in the event queue 306, while in other embodiments the checkpoint data can be analyzed and the relevant process or state data written to a process data store 310, from which the state data can be retrieved.

As with the earlier event data in the event queue 306, eventually the frontend 304 or a worker manager 312 will allocate an instance to process the event and will pass the event data to the instance for processing using the appropriate registered function. In this example a restore manager 308 can be contacted to obtain the relevant state data (or other processing or checkpoint data) from the process data store 310 to provide to the worker, in order to restore the worker to a state where the worker can pick up where the prior processing left off for the event. In at least some embodiments the restore manager 308 will ensure the restoration of state before releasing the event for processing, and if the state cannot be restored then another attempt can be made, another worker allocated, or another such action taken. Once the state is restored, the processing for the event can resume using the allocated instance.

As mentioned the process can continue, with the event data being redelivered to workers each time checkpoint data is received, until the processing is completed, at which point the frontend 304 can return the result(s). The ability to keep redelivering the event data can be problematic, however, as it is possible that a code bug or other unintended occurrence may cause the event data to be redelivered in a never-ending loop, which can occupy resources and generate undesired expense. Accordingly, there can be various limits put in place to limit the number of redeliveries or amount of processing time allocated for a given event, customer, or function, etc.

For example, a customer might specify a rule or policy indicating a maximum number of retries or redeliveries to be performed for an event. This can be for all functions for that customer, for specific functions, for specified types of events, or for other such criteria. In some embodiments the customer can specify the number of retries in the event data, the request, or the function as well, among other such options. The resource provider might also provide a maximum number of retries, or at least require that customers specify a maximum number of retries or other such limit. The number of retries allowed in some embodiments can depend at least in part upon the current workload or capacity of the environment. In some embodiments there may be a limit to the number of concurrently executing resources, which can also impact the number of retries available for an event.

The customer can also, or alternatively, specify a maximum amount of processing to be performed for a given event. This can be per worker or cumulative across all workers for a given event. For example, a customer might not want more than five or ten minutes of processing cumulatively to occur for a given event, after which the processing should cease and resources allocated to processing other events. The time periods can be much shorter as well, such as on the order of seconds, or tens of seconds, or less. More complex rules or policies can be implemented as well such as combinations of attempts and time, as may vary with workload or the concurrent number of customer events, etc.

FIG. 4 illustrates an example process 400 for processing a registered function for an event using one or more allocated resource instances that can be utilized in accordance with various embodiments. It should be understood for this and other processes discussed herein that there can be additional, alternative, or fewer steps performed in similar or alternative orders, or in parallel, within the scope of the various embodiments unless otherwise stated. In this example, information for a customer event is received 402 to a resource allocation service or other appropriate system or offering. The information can be received from a customer request or in response to detecting a specified type of event among other such options. A registered function associated with that type of event that is to be used to process the event can be determined 404. A customer can specify types of functions for types of events, can provide guidelines as to which functions to use, or can specify sources or other criteria for use in determining the appropriate registered function in accordance with various embodiments.

In this example, the event information can be placed 406 into an event queue for processing. Information for the corresponding registered function can be included with the event information or associated with the event information in some way, such that an appropriate resource instance or worker can be selected to process the event. This can include a warmed instance that is already configured and available to process that type of event using the corresponding function, or can involve initializing or reconfiguring a new instance, among other such options. The events can be processed from the queue in any appropriate order, such as by using a FIFO or LIFO approach or selecting based on priority or type, among other such options. At some point it can be determined 408 that there is an available resource instance (e.g., virtual machine or container) for processing the event information using the registered function. The instance can then be allocated 410 for processing the event, and the event can be processed until processing by that instance has completed and a result of the processing is received 412.

As mentioned, it might be the case that all processing for the event has not completed even though the processing by that particular instance may have completed. This can be due to the fact that a maximum processing time was reached by the instance, or that a break point in the event was reached, among other such options discussed and suggested herein. As a result the event may require at least some additional amount of processing. Accordingly, the result received from processing by the instance may include some amount of checkpoint data indicating that additional processing is needed. As discussed herein, the checkpoint data can include information such as state data for the resource instance prior to termination of processing by the instance. In this way, the next instance allocated to process the event can have the appropriate state information restored in order to resume processing by the allocated instance. Other information can be included as well, as discussed and suggested herein. This additional information can include, for example, instructions for use of different or additional functions for portions of the additional processing. In at least some embodiments the instructions can also request concurrent processing of different portions of the event, such as wherein an initial resource allocation performs the appropriate pre-processing then multiple resource instances are allocated to handle the subsequent process portions. A determination can be made 414 when a result is received as to whether there is checkpoint data received with the result. If not, the result of the event processing (or data associated with the result) can be provided 416 to the appropriate location or device, as may be associated with the corresponding customer. If checkpoint data is received with the result, the event information and checkpoint data can be caused 418 to be placed back in the event queue, enabling the event to have one or more additional resources instances allocated in order to complete processing for the event.

As mentioned, however, it might be the case that an error or malicious code causes redelivery requests to be received repeatedly for an event, which can result in an infinite loop (or similar occurrence) which can undesirably tie up resources for a significant period of time. Accordingly, approaches in accordance with various embodiments can attempt to prevent (or minimize the impact of) such occurrences while enabling a sufficient number of retries to be performed for legitimate customer events. FIG. 5 illustrates one such example process 500 that can be utilized to process registered events in accordance with various embodiments. In this example, a resource instance is allocated 502 to process an event using a determined registered function, such as is discussed with respect to FIG. 4. As mentioned, information for the event can have been placed in an event queue, and the event information can have been pulled from the queue for processing when an appropriate resource instance is available, or when a new instance can be created in order to process the event. The resource instance can process the event as discussed herein, and at an end of processing by the instance a result or response can received 504. As mentioned, this can include result data for the processing and any other appropriate data, script, configuration, or function data that may be produced through the processing of the function by the resource instance.

It may be the case, however, that all processing for the event has not completed, and the allocated instance was only able to perform a subset of the processing. As mentioned, this might be due to a maximum processing time limit for allocated instances, a breakpoint in the registered function, or another such occurrence. Accordingly, checkpoint data might be received with (or otherwise indicated by) the result data. If it is determined 506 that no checkpoint data was received, and therefore processing for the event has completed, then the result of the processing can be provided 508, such as by providing result data for successful completion or an error message if the processing could not be performed. If checkpoint data is received, such that additional processing and/or redelivery is requested, then a couple of additional determinations might be made before determining whether to continue the processing. In this example, a determination can be made 510 as to whether a maximum number of retries or redeliveries, or maximum number of instance allocations, etc., has been reached or exceeded for the event. As mentioned, in some embodiments a customer may specify a maximum number of redeliveries or reallocations before processing is terminated for an event and resources are allocated for other events. There can be a counter associated with an event in some embodiment that gets incremented each time a resource processes a portion of the event, and this counter can be analyzed upon a result being provided or upon a redelivery being attempted. A benefit to checking whether a number of retries would allow for another redelivery upon getting the result data is that an event would not be placed in the queue and analyzed if no further processing is permitted. Other such rules or policies may apply as well. If such a maximum number has been reached then processing for the event can be terminated 512 and a notification provided 514 for the event. The notification can include, for example, an error message, a customer communication, a record written to a log or data repository, etc. Similarly, a determination can be made 516 in some embodiments as to whether a maximum overall processing time has been met or exceeded. For example, a customer might not want to pay for more than five minutes of processing for an event of a specified type, and if processing for an event will pass the five minute mark then the processing should be terminated regardless of the amount of progress made, although in some embodiments a combination of progress or checkpoints can be used with the time limits such that events are not terminated if there are almost completely processed, within specified limits, etc. A delivery manager or other such component can be responsible for managing various clocks or counters relating to processing times or redeliveries, etc. If the maximum time has been reached or exceeded then the processing for the event can be terminated and error notification returned as discussed previously. If the maximum number of retries and/or maximum amount of time has not been reached then the event information and checkpoint data can be placed 518 in the event queue for further processing. This process can continue until the event processing is completed or until one of the processing thresholds has been reached, among other such options. If a termination point or value is reached, notification can be provided to the function and/or resource instance indicating that processing is to be terminated.

In various embodiments the resource allocation system will not care what is contained within the checkpoint data. The checkpoint data can include internal function state data, references to other functions or state information, a list of requirements for continued processing, or other such information. From the system or service perspective, however, the configuration data can be an opaque object whose data values or contents do not matter, as long as the presence and format of the configuration data are such to indicate that further processing is needed for the event.

In order to enable further processing of an event, there can be multiple function entry points. Conventional processing approaches might utilize a single handler function in a function API as a point of entry. Another entry point can allow for termination instructions to be received, as well as other such instructions. The function can then capture a snapshot, or otherwise determine the information for the checkpoint data, and then generate the result and checkpoint data to be returned, as well as when to terminate the processing (instantly or at the next logical point, etc.). The instance can thus terminate processing in such a way that the appropriate data is captured and forwarded for subsequent processing. In some embodiments the checkpoint data can include both the appropriate records and information identifying the type(s) of those records. The types can be any appropriate types, such as may refer to the memory state of a virtual module, data for a disc allocation, specific files or folders on the platform, etc. If the checkpoint data includes a link to an external index or other data object, the information can be retrieved and passed along with the event data. When the data is received, the function (or instance executing the function) can determine the types of data or records and process the data as appropriate, including restoring state, updating configuration, or performing other such actions. The function implementation thus can be responsible for understanding the contents of the checkpoint data and how to utilize that data to continue processing the event. In some embodiments a different events queue can be used for redelivery, with resources being allocated that are able to handle the redelivery attempts, or can utilize a different priority scheme, etc. Because redeliveries relate to events that are more likely to utilize a higher amount of processing, those events can be processed using a different pool of resources in at least some embodiments. In some embodiments data for events that require redelivery can be logged or otherwise tracked in order to determine the presence of bugs in the code or other such issues. The tracking of redeliveries and processing attempts can also be used to enforce other limitations as well, such as a maximum number of concurrently executing resource instances or concurrent number of queued events, etc. The system can also monitor the average number of retries or length of processing for a type of event such that a customer can determine the likelihood of a problem or other such occurrence. There may also be overall length of time criteria as well, or maximum length between processing allocations, etc. A customer can potentially utilize a dedicated API or other such mechanism to disable or modify the redelivery process at any time. The delivery modification could be for certain types of events or processing, among other such options.

FIG. 6 illustrates a set of basic components of an example computing device 600 that can be utilized to implement aspects of the various embodiments. In this example, the device includes at least one processor 602 for executing instructions that can be stored in a memory device or element 604. As would be apparent to one of ordinary skill in the art, the device can include many types of memory, data storage or computer-readable media, such as a first data storage for program instructions for execution by the at least one processor 602, the same or separate storage can be used for images or data, a removable memory can be available for sharing information with other devices, and any number of communication approaches can be available for sharing with other devices. The device may include at least one type of display element 606, such as a touch screen, electronic ink (e-ink), organic light emitting diode (OLED) or liquid crystal display (LCD), although devices such as servers might convey information via other means, such as through a system of lights and data transmissions. The device typically will include one or more networking components 608, such as a port, network interface card, or wireless transceiver that enables communication over at least one network. The device can include at least one input device 610 able to receive conventional input from a user. This conventional input can include, for example, a push button, touch pad, touch screen, wheel, joystick, keyboard, mouse, trackball, keypad or any other such device or element whereby a user can input a command to the device. These I/O devices could even be connected by a wireless infrared or Bluetooth or other link as well in some embodiments. In some embodiments, however, such a device might not include any buttons at all and might be controlled only through a combination of visual and audio commands such that a user can control the device without having to be in contact with the device.

As discussed, different approaches can be implemented in various environments in accordance with the described embodiments. As will be appreciated, although a Web-based environment is used for purposes of explanation in several examples presented herein, different environments may be used, as appropriate, to implement various embodiments. The system includes an electronic client device, which can include any appropriate device operable to send and receive requests, messages or information over an appropriate network and convey information back to a user of the device. Examples of such client devices include personal computers, cell phones, handheld messaging devices, laptop computers, set-top boxes, personal data assistants, electronic book readers and the like. The network can include any appropriate network, including an intranet, the Internet, a cellular network, a local area network or any other such network or combination thereof. Components used for such a system can depend at least in part upon the type of network and/or environment selected. Protocols and components for communicating via such a network are well known and will not be discussed herein in detail. Communication over the network can be enabled via wired or wireless connections and combinations thereof. In this example, the network includes the Internet, as the environment includes a Web server for receiving requests and serving content in response thereto, although for other networks, an alternative device serving a similar purpose could be used, as would be apparent to one of ordinary skill in the art.

The illustrative environment includes at least one application server and a data store. It should be understood that there can be several application servers, layers or other elements, processes or components, which may be chained or otherwise configured, which can interact to perform tasks such as obtaining data from an appropriate data store. As used herein, the term “data store” refers to any device or combination of devices capable of storing, accessing and retrieving data, which may include any combination and number of data servers, databases, data storage devices and data storage media, in any standard, distributed or clustered environment. The application server can include any appropriate hardware and software for integrating with the data store as needed to execute aspects of one or more applications for the client device and handling a majority of the data access and business logic for an application. The application server provides access control services in cooperation with the data store and is able to generate content such as text, graphics, audio and/or video to be transferred to the user, which may be served to the user by the Web server in the form of HTML, XML or another appropriate structured language in this example. The handling of all requests and responses, as well as the delivery of content between the client device and the application server, can be handled by the Web server. It should be understood that the Web and application servers are not required and are merely example components, as structured code discussed herein can be executed on any appropriate device or host machine as discussed elsewhere herein.

The data store can include several separate data tables, databases or other data storage mechanisms and media for storing data relating to a particular aspect. For example, the data store illustrated includes mechanisms for storing content (e.g., production data) and user information, which can be used to serve content for the production side. The data store is also shown to include a mechanism for storing log or session data. It should be understood that there can be many other aspects that may need to be stored in the data store, such as page image information and access rights information, which can be stored in any of the above listed mechanisms as appropriate or in additional mechanisms in the data store. The data store is operable, through logic associated therewith, to receive instructions from the application server and obtain, update or otherwise process data in response thereto. In one example, a user might submit a search request for a certain type of item. In this case, the data store might access the user information to verify the identity of the user and can access the catalog detail information to obtain information about items of that type. The information can then be returned to the user, such as in a results listing on a Web page that the user is able to view via a browser on the user device. Information for a particular item of interest can be viewed in a dedicated page or window of the browser.

Each server typically will include an operating system that provides executable program instructions for the general administration and operation of that server and typically will include computer-readable medium storing instructions that, when executed by a processor of the server, allow the server to perform its intended functions. Suitable implementations for the operating system and general functionality of the servers are known or commercially available and are readily implemented by persons having ordinary skill in the art, particularly in light of the disclosure herein.

The environment in one embodiment is a distributed computing environment utilizing several computer systems and components that are interconnected via communication links, using one or more computer networks or direct connections. However, it will be appreciated by those of ordinary skill in the art that such a system could operate equally well in a system having fewer or a greater number of components than are illustrated. Thus, the depiction of the systems herein should be taken as being illustrative in nature and not limiting to the scope of the disclosure.

The various embodiments can be further implemented in a wide variety of operating environments, which in some cases can include one or more user computers or computing devices which can be used to operate any of a number of applications. User or client devices can include any of a number of general purpose personal computers, such as desktop or notebook computers running a standard operating system, as well as cellular, wireless and handheld devices running mobile software and capable of supporting a number of networking and messaging protocols. Devices capable of generating events or requests can also include wearable computers (e.g., smart watches or glasses), VR headsets, Internet of Things (IoT) devices, voice command recognition systems, and the like. Such a system can also include a number of workstations running any of a variety of commercially-available operating systems and other known applications for purposes such as development and database management. These devices can also include other electronic devices, such as dummy terminals, thin-clients, gaming systems and other devices capable of communicating via a network.

Most embodiments utilize at least one network that would be familiar to those skilled in the art for supporting communications using any of a variety of commercially-available protocols, such as TCP/IP, FTP, UPnP, NFS, and CIFS. The network can be, for example, a local area network, a wide-area network, a virtual private network, the Internet, an intranet, an extranet, a public switched telephone network, an infrared network, a wireless network and any combination thereof.

In embodiments utilizing a Web server, the Web server can run any of a variety of server or mid-tier applications, including HTTP servers, FTP servers, CGI servers, data servers, Java servers and business application servers. The server(s) may also be capable of executing programs or scripts in response requests from user devices, such as by executing one or more Web applications that may be implemented as one or more scripts or programs written in any programming language, such as Java®, C, C # or C++ or any scripting language, such as Perl, Python or TCL, as well as combinations thereof. The server(s) may also include database servers, including without limitation those commercially available from Oracle®, Microsoft®, Sybase® and IBM® as well as open-source servers such as MySQL, Postgres, SQLite, MongoDB, and any other server capable of storing, retrieving and accessing structured or unstructured data. Database servers may include table-based servers, document-based servers, unstructured servers, relational servers, non-relational servers or combinations of these and/or other database servers.

The environment can include a variety of data stores and other memory and storage media as discussed above. These can reside in a variety of locations, such as on a storage medium local to (and/or resident in) one or more of the computers or remote from any or all of the computers across the network. In a particular set of embodiments, the information may reside in a storage-area network (SAN) familiar to those skilled in the art. Similarly, any necessary files for performing the functions attributed to the computers, servers or other network devices may be stored locally and/or remotely, as appropriate. Where a system includes computerized devices, each such device can include hardware elements that may be electrically coupled via a bus, the elements including, for example, at least one central processing unit (CPU), at least one input device (e.g., a mouse, keyboard, controller, touch-sensitive display element or keypad) and at least one output device (e.g., a display device, printer or speaker). Such a system may also include one or more storage devices, such as disk drives, optical storage devices and solid-state storage devices such as random access memory (RAM) or read-only memory (ROM), as well as removable media devices, memory cards, flash cards, etc.

Such devices can also include a computer-readable storage media reader, a communications device (e.g., a modem, a network card (wireless or wired), an infrared communication device) and working memory as described above. The computer-readable storage media reader can be connected with, or configured to receive, a computer-readable storage medium representing remote, local, fixed and/or removable storage devices as well as storage media for temporarily and/or more permanently containing, storing, transmitting and retrieving computer-readable information. The system and various devices also typically will include a number of software applications, modules, services or other elements located within at least one working memory device, including an operating system and application programs such as a client application or Web browser. It should be appreciated that alternate embodiments may have numerous variations from that described above. For example, customized hardware might also be used and/or particular elements might be implemented in hardware, software (including portable software, such as applets) or both. Further, connection to other computing devices such as network input/output devices may be employed.

Storage media and other non-transitory computer readable media for containing code, or portions of code, can include any appropriate media known or used in the art, such as but not limited to volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data, including RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices or any other medium which can be used to store the desired information and which can be accessed by a system device. Based on the disclosure and teachings provided herein, a person of ordinary skill in the art will appreciate other ways and/or methods to implement the various embodiments.

The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. It will, however, be evident that various modifications and changes may be made thereunto without departing from the broader spirit and scope of the invention as set forth in the claims. 

What is claimed is:
 1. A computer-implemented method, comprising: detecting a notification event associated with a customer of a multi-tenant resource allocation service; determining a registered function corresponding to the notification event, the registered function including code to be executed on behalf of the customer; placing event information for the notification event in an event queue; allocating a first resource instance for executing the registered function to process the notification event, the first resource instance obtaining the event information from the event queue; receiving, from the first resource instance, a processing result for the notification event; determining that checkpoint data is included with the processing result, the checkpoint data including state data for the first resource instance prior to termination of processing and indicating a request for further processing; placing, based at least in part on determining that the checkpoint data is included with the processing result, the event information and the checkpoint data in the event queue; allocating at least a second resource instance to perform additional processing for the notification event; providing the checkpoint data to the second resource instance, wherein the state data is restored to the second resource instance for the additional processing; receiving, from the second resource instance, a second processing result; determining that additional checkpoint data is not included with the second processing result; and providing, based at least in part on determining that the additional checkpoint data is not included with the second processing result, the second processing result received from the second resource instance.
 2. The computer-implemented method of claim 1, further comprising: allocating an additional resource instance to perform the additional processing for the notification event until processing for the notification event is completed or would violate one or more processing criteria.
 3. The computer-implemented method of claim 1, further comprising: determining that a maximum processing time for the first resource instance has been met; capturing a data snapshot representing the state data for the first resource instance prior to termination of processing; and including the data snapshot, or a reference to the data snapshot, with the checkpoint data.
 4. The computer-implemented method of claim 1, further comprising: determining one or more processing criteria based at least in part upon a type of the notification event, the one or more processing criteria including at least one of a maximum number of instance allocations, a maximum number of redeliveries, or a maximum overall processing time for the type of the notification event.
 5. A computer-implemented method, comprising: determining an event associated with a registered function; placing event data in a queue, the event data associated with the event; allocating a first resource instance, of a plurality of resource instances of a resource allocation service, to execute the registered function on the event data in order to process the event, the first resource instance obtaining the event data from the queue; receiving a processing response from the first resource instance; determining that the processing response includes checkpoint data indicating a request for further processing for the event; placing the event data and the checkpoint data in the queue; allocating, based at least in part on determining that the processing response includes the checkpoint data, a second resource instance to execute the registered function; providing the checkpoint data to the second resource instance, the second resource instance restoring an execution state of the first resource instance using the checkpoint data; receiving a second processing response from the second resource instance; determining that the checkpoint data is not included with the second processing response; and providing, based at least in part on determining that the checkpoint data is not included with the second processing response, a result of the processing for the event.
 6. The computer-implemented method of claim 5, further comprising: sequentially allocating one or more additional resource instances to perform additional processing for the event until processing for the event is completed or no further processing is allowed for the event using the plurality of resource instances.
 7. The computer-implemented method of claim 6, further comprising: determining that further processing is prevented for the event according to at least one of a maximum number of redeliveries or a maximum amount of processing time for the event.
 8. The computer-implemented method of claim 5, further comprising: placing the event data in a first event queue before allocating the first resource instance; and placing the event data and the checkpoint data in a second event queue before allocating the second resource instance, the second event queue being implemented via the first event queue.
 9. The computer-implemented method of claim 5, wherein the first resource instance and the second resource instance are each one of a virtual machine or a respective container executing on at least one virtual machine.
 10. The computer-implemented method of claim 5, further comprising: determining that a maximum processing time for the first resource instance has been met; capturing a data snapshot representing state data for the first resource instance prior to termination of processing; and including the data snapshot or a reference to the data snapshot with the checkpoint data.
 11. The computer-implemented method of claim 5, wherein the checkpoint data further includes one or more instructions for performing additional processing.
 12. A system, comprising: at least one processor; and memory including instructions that, when executed by the at least one processor, cause the system to: determine an event associated with a registered function; place event data in a queue, the event data associated with the event; allocate a first resource instance, of a plurality of resource instances of a resource allocation service, to execute the registered function on event data in order to process the event; receive a processing response from the first resource instance; determine that the processing response includes checkpoint data indicating a request for further processing for the event; place the event data and the checkpoint data in the queue; allocate, based at least in part on determining that the processing response includes the checkpoint data, a second resource instance to execute the registered function; provide the checkpoint data to the second resource instance, the second resource instance restoring an execution state of the first resource instance using the checkpoint data; receive a second processing response from the second resource instance; determine that the checkpoint data is not included with the second processing response; and provide, based at least in part on determining that the checkpoint data is not included with the second processing response, a result of the processing for the event.
 13. The system of claim 12, wherein the instructions when executed further cause the system to: sequentially allocate one or more additional resource instances to perform additional processing for the event until processing for the event is completed or no further processing is allowed for the event using the plurality of resource instances.
 14. The system of claim 13, wherein the instructions when executed further cause the system to: determine that no further processing is allowed for the event according to at least one of a maximum number of redeliveries or a maximum amount of processing time for the event.
 15. The system of claim 12, wherein the instructions when executed further cause the system to: place the event data in a first event queue before allocating the first resource instance; and place the event data and the checkpoint data in a second event queue before allocating the second resource instance, the second event queue being implemented via the first event queue.
 16. The system of claim 12, wherein the first resource instance and the second resource instance are each one of a virtual machine or a respective container executing on at least one virtual machine.
 17. The system of claim 12, wherein the instructions when executed further cause the system to: determine that a maximum processing time for the first resource instance has been met; capture a data snapshot representing state data for the first resource instance prior to termination of processing; and include the data snapshot or a reference to the data snapshot with the checkpoint data. 